JP2002301543A - Method for molding sand mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method with which a mold using no pattern plate and having small amount of binder and little deformation, can be molded. SOLUTION: This method is contained of a laminating process for thinly laminating the sand; a process for manufacturing the thin sand laminated body by drawing the outer shape of an one thin piece among many thin pieces generated when slicing a casting to be produced by pouring gas hardening agent with a pouring means, and pouring the gas hardening agent to the outer peripheral part of the laminated sand, too; a process for manufacturing a three-dimensional sand laminated material 7 composed of many sand laminated bodies by repeating the above processes to the other thin pieces, too, among many thin pieces; processes 5, 5a for hardening the gas hardening agent by passing the hardening gas through this sand laminated material; and a process for removing the sand at the outside in a portion surrounded with the gas hardening agent in the sand laminated material. In this way, the sand mold having a necessary cavity for casting can be molded.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for manufacturing a thin sand laminate by pouring a gas hardening agent onto a thinly laminated sand so as to draw a contour of a predetermined shape. The present invention relates to a method for producing a three-dimensional sand laminate comprising a laminate, flowing a hardening gas and hardening a gas hardener to form a sand mold.

[0002]

2. Description of the Related Art Conventionally, a mold plate is made of a wooden mold or a metal mold, and the mold is formed by inverting the mold plate based on the mold plate. Therefore, a model plate is required regardless of the number of mold molds. And Furthermore, the model plate had to be stored and maintained in preparation for molding the mold again. As a conventional technique for directly molding a mold, a method has been developed in which a cavity is formed by cutting a previously created mold block to form a mold (Ohashi, Inoue: Jakuto News (198)
1) No5, p25) In this mold making method, the cut part was turned into waste and needed to be regenerated. In addition, the mold making apparatus for this purpose does not have CAM software that can directly process the three-dimensional CAD data, and it is necessary to newly build an NC program by an automatic professional, which requires much time and labor.

[0003] Further, since a normal casting mold basically uses molding sand coated with a binder, it is necessary to break the casting mold in order to remove the casting from the casting mold after casting. However, the mold cannot be disposed of only the part that has been thermally degraded in contact with the casting, and it is necessary to destroy and dispose of the entire used mold. Further, in a mold used for casting a large casting or a thin casting, since a wooden model plate cannot be deformed by casting sand to transfer a correct shape, a mold may be required in some cases.

[0004] Further, as a method of directly forming a mold without a model plate, a method of jetting a binder to silica sand or the like formed in a required shape and fixing the same, or a method using a molding sand coated with a thermosetting resin as a binder by a laser. There is a method of bonding by heating.

[0005] The former is a method of forming a precision casting mold by spraying colloidal silica, heat-transfer drying, and solidifying a thin layer of silica sand or the like for molding the mold, and solidifying a slice-shaped portion of the cross section of the mold. . In this mold making method, it is necessary to dry the mold every time the binder is injected, and it takes a long time to make the mold, and the lamination and drying are performed sequentially, so that there is a problem that the deformation in the thin portion cannot be completely prevented. In the latter case, since the laser is used for heating, the binder is overheated and dissipated, and therefore, it is necessary to use a larger amount of the binder than in the case of using a normal heating mold. Moreover,
Since sufficient hardening strength cannot be obtained, it is necessary to carefully remove the coating sand in the hollow portion for producing the casting and then heat the whole to develop sufficient strength.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method capable of forming a mold having a small amount of binder and a small deformation without using a model plate. It is in.

[0007]

According to a first aspect of the present invention, there is provided a method for forming a sand mold, wherein a laminating step of laminating a thin layer of sand and a gas hardening agent are poured out on the laminated sand by a pouring means. Manufacturing a thin sand laminate by drawing the outer shape of one of the thin flakes generated when the casting is sliced and pouring the gas curing agent also to the outer periphery of the laminated sand; and A step of producing a three-dimensional sand laminate composed of a large number of sand laminates by repeating the above steps for other flakes of the flakes, and flowing the curing gas through the sand laminate to form the gas curing agent. Curing, and removing the sand outside the portion of the sand laminate surrounded by the gas hardener, thereby forming a sand mold having a required casting cavity. I do.

According to a second aspect of the present invention, there is provided a method for forming a sand mold, comprising: a laminating step of laminating a thin layer of sand; and slicing a core to be produced by pouring a gas hardener onto the laminated sand by a pouring means. A step of drawing the outline of one of the thin flakes out of a large number of flakes that occur in the case of and producing a thin sand laminate,
A step of producing a three-dimensional sand laminate composed of a large number of sand laminates by repeating the above steps for the other flakes among the large number of flakes, and flowing a curing gas through the sand laminate to cure the gas. Curing the agent, and removing sand outside the portion of the sand laminate surrounded by the gas curing agent, thereby producing a core having a required shape. And

In the present invention, the sand mold means a main mold and a core. In addition, in the present invention, as a method of curing a gas curing agent by flowing a curing gas, there are a mold molding by a cold box method and a CO ₂ mold molding method.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to FIGS. As shown in FIG.
Sand 3 is laminated thinly on the upper surface of an air-permeable and plate-shaped worktable 1 such as a wire mesh, punched metal, or a porous material by a sand dispersing device 2. The gas hardening agent 5a is drawn out, and the outline of one of the thin flakes generated when the casting to be manufactured is sliced is drawn, and the gas hardening agent 5a is also poured out to the outer peripheral portion of the laminated sand. To produce a thin sand laminate (see Figure 1). Next, the above steps are repeated for the other thin pieces among the above-mentioned many thin pieces to produce a three-dimensional sand laminate 7 including a large number of sand laminates 6 as shown in FIG.

Next, as shown in FIG. 3, after covering the sand laminate 7 and the work table 1 with a cover member 8, the inside of the cover member 8 is depressurized. Subsequently, a hardening gas is sucked into the cover member 8. The curing gas flows through the gas curing agent 5.5a of the sand laminate 7 to harden the gas curing agent 5.5a. Then
After removing the cover member 8, the sand 9 outside the portion of the sand laminate 7 surrounded by the gas hardener 5 is removed.
Thereby, as shown in FIG. 4, a sand mold 11 having a predetermined casting cavity 10 can be obtained.

[0012]

EXPERIMENTAL EXAMPLE 1 Hereinafter, an experimental example of the present invention will be described. The used mold sand was sprayed on a stainless steel vat through a 590 μ (28 mesh) sieve using AFS70 (JIS120). Water glass (Fuji Chemical, VR-T) was diluted with water as a binder, dropped with a pipette, and absorbed by capillary action.

[0013]

【table 1】

Thereafter, the bat was placed together with the vat in a vacuum chamber, and the pressure was reduced by a rotary pump. Thereafter, carbon dioxide gas was blown at 2 L / min until a normal pressure was reached, and the gas was taken out into the atmosphere after 5 min. When the amount of the binder is large, the mold material is permeated, and when the amount is small, the material is broken during handling.
Sufficient mold retention was confirmed at a dilution ratio of about 0.1 to 0.06 (solid content of 5 to 1.5%).

[0015]

[Experimental Example 2] Sand was spread over a polyethylene cup, and a binder was applied in a circular shape constituting a bottom surface. 1cm more
After spreading the sand, apply the binder in an arc shape,
After repeating three times, it was placed in a vacuum chamber and depressurized. Decompression reaches 18 Toor in about 1 minute, holds for about 1 minute, introduces carbon dioxide gas at 3ι / min, holds at 200 Toor for 1 minute,
Hold at rr for 5 minutes. The uncured powder was removed to obtain a cup-shaped cured product.

[0016]

[Experimental example 3] The mold sand used was 590μ with AFS70 (JIS120).
(28 mesh) and sprayed on a stainless steel vat. Water-soluble phenolic resin (Kobe Rikagaku Kogyo,
PHENIX-1000) was diluted with water, dropped with a pipette, and absorbed by capillary action.

[0017]

[Table 2]

Since the solid content of the resin is unknown, the weight of the filter paper impregnated with the binder and dried and solidified in advance, and the filter paper impregnated with the binder and cured with carbon dioxide, were measured and measured. However, the solid content was 60%, and the weight increased by about 12% due to the hardening of carbon dioxide gas.

[0019]

Experimental Example 4 Test pieces of 10 × 10 × 100 and 20 × 20 × 100 mm were produced in accordance with Case 3 for measuring the strength of the cured product. However, the former was made by laminating once, and the latter was made by laminating four times.
As shown in FIG. 5, the bending strength depends on the solid content in the binder. When the number of laminations was increased and the lamination height was reduced, the lamination was repeated, and the binder was repeatedly added. Therefore, it was recognized that the strength was increased even with the same solid content.

[0020]

As is apparent from the above description, the present invention provides a laminating step of laminating sand thinly,
The gas curing agent is drawn out by the pouring means, and the gas curing agent is drawn on the outer periphery of the laminated sand by drawing the outline of one of the flakes generated when the casting to be produced is sliced. Producing a three-dimensional sand laminate comprising a plurality of sand laminates by repeating the above steps for the other flakes among the plurality of flakes; and Flowing a curing gas through the laminate to cure the gas curing agent, and removing sand outside a portion of the sand laminate surrounded by the gas curing agent, whereby the required Since it is possible to mold the sand mold with the casting cavity of the mold, it is possible to save the trouble of model production that was conventionally required when making the mold, and to prevent the poor shape transfer caused by the deformation of the model at the time of mold production. Achieve the practical effect that.

[Brief description of the drawings]

FIG. 1 is a front view of an explanatory view for explaining a process of one embodiment of the present invention.

FIG. 2 is a front view of an explanatory view for explaining a process of one embodiment of the present invention.

FIG. 3 is a front view of an explanatory view for explaining a process of one embodiment of the present invention.

FIG. 4 is a front view of an explanatory view for explaining a process of one embodiment of the present invention.

Fig. 5 Effect of binder amount on bending strength (2 levels)
FIG.

Claims (3)

[Claims] Claims: 1. A laminating step of laminating sand thinly, and a laminating process of pouring a gas hardener by a pouring means onto the laminating sand to slice a casting to be produced. A step of drawing the outer shape and pouring the gas curing agent also to the outer peripheral portion of the laminated sand to produce a thin sand laminate, and repeating the above steps for the other flakes of the multitude of flakes, Producing a three-dimensional sand laminate consisting of the sand laminate, flowing a curing gas through the sand laminate to cure the gas curing agent, and surrounding the gas laminate with the gas curing agent in the sand laminate. Removing the sand outside the set portion, thereby forming a sand mold having a required casting cavity. 2. A laminating step of laminating sand thinly, and one of a number of laminae produced when a core to be produced is sliced by pouring a gas hardening agent onto the laminated sand by a pouring means. A step of drawing a contour and manufacturing a thin sand laminate, and a step of manufacturing a three-dimensional sand laminate composed of a large number of sand laminates by repeating the above steps for the other flakes among the plurality of flakes. A step of allowing the curing gas to flow through the sand laminate to cure the gas curing agent, and a step of removing sand outside a portion of the sand laminate surrounded by the gas curing agent, A method for producing a core having a required shape. 3. The method for molding a sand mold according to claim 1, wherein the flow of the hardening gas is performed by suction under reduced pressure.